1. Field of the Invention
The present invention relates to an inkjet ejection apparatus, an inkjet ejection method and an inkjet recording apparatus, and more particularly to inkjet ejection technology for forming dots of a plurality of sizes.
2. Description of the Related Art
In an inkjet recording apparatus forming a desired image on a recording medium by using an inkjet method, a drive method is known which, in order to form dots of a plurality of sizes, operates a drive element, such as a piezoelectric element, by selecting one or more drive waveforms corresponding to a desired dot size from common drive waveforms having waveforms corresponding to a plurality of dot sizes.
Japanese Patent Application Publication No. 11-348320 discloses an inkjet ejection apparatus including: a generating device which outputs a reference signal in which ejection pulses for performing one ejection action are joined together a maximum number of times at prescribed time intervals and which also includes a non-ejecting pulse to drive an actuator so as to cancel out pressure wave vibration inside an ink chamber after an interval that enables the pressure wave vibration inside the ink chamber to be substantially cancelled out, from the last ejection pulse of the maximum number of times; and a correction device which outputs an application drive signal for application to an actuator by removing an unwanted portion of the reference signal in accordance with a number of ejection actions specified in respect of the print data for one dot, wherein the application drive signal is output by removing a prescribed number of ejection pulses which constitute the reference signal, sequentially from the start.
However, the swelling of the meniscus after ejecting a prescribed number of droplets differs between a case where a dot (a dot of minimum size) is formed by ejection in which a single pulse is applied, and a case where a dot (a dot of maximum size, for example) is formed by ejection in which a plurality of pulses are consecutively applied. For example, the swelling of the meniscus after ejection when five pulses have been consecutively applied is clearly greater than when a single pulse has been applied. Since the meniscus after ejection when a single pulse has been applied rarely shows large oscillation sufficient to affect the next ejection operation, then application of a non-ejection pulse to cancel out pressure wave vibration inside the ink chamber is not necessary. On the other hand, a satellite droplet is liable to occur after ejection by application of a single pulse and there is a risk that the shape of the droplet (and the resulting dot) may deform due to the occurrence of satellite.
More specifically, in the ejection technology disclosed in Japanese Patent Application Publication No. 11-348320, the state of swelling of the meniscus varies with the number of pulses having been applied, but since the same non-ejection pulse is used for any number of pulses, the technology cannot be considered to respond sufficiently to all states of swelling of the meniscus. Moreover, when a single pulse is applied or a small number of pulses are consecutively applied, there is a risk of deterioration of the dot shape due to the occurrence of satellite, and therefore a countermeasure of some kind is necessary in order to suppress the occurrence of satellite.